Composite board structure



Patented July 20, 1943 Application August 20, 19111,` SeralNo. 407,677

l ,e `In Sweden February '7, 1941 1 claim. (c1. 20-91) The present invention :relates to,` Acomposite board structures of the kind which ,are'composed of a plurality of wood layers glued together, said layers comprising an upper parquetveneer layer', a filling or intermediate layerand a lower cover- In Figures l and 2 two boards joined together are shown, the parquet veneer 'layer and the upper binding layer having been removed from one e of the boards for the purposeof showingjthe ing layer. For obtaining the greatestpossible, bending strength, which is important in cases` where such boards are to be used as a flooring, the lower covering layer, which, when loaded, is

`exposed to tensile stresses, should have its run `of grain extending in the longitudinal directions.`

of the board. From the point of view of strength,

also the filling layer should, preferably, have its libres extending in the longitudinal direction of the board, saidflling layer being suitably composed of a number of rods parallel tothe longi-,H tudinal direction of the board. The present in' vention has for itsj object to 'provide a board structure ofethisekind resistant to moisture and temperature variations, and particularly it has for its object to prevent such displacements in the transversal direction of the board as may arise in layers, having longitudinal run of grain, on account of the swelling or drying of the wood. It is known to form, for that purpose, the filling layer `of lengths having their run of grain extending in the transversal direction of the board. However, such an arrangement of the filling layer is unsuitable from the point of view of strength. According to the present invention, the binding of the layers in the transversal direction is obtained by one or more binding layers,of veneer, the run of grain of which extends in `the transversal direction of the board, being arranged between the outer layers on either or both sides of the filling layer. ranged, in the `first place, between the parquet veneer layer and the filling layer,'whereby an effective binding of the parquet veneer rods in the transversal direction of the board is obtained, while at the same time the lengths of the filling layer are bound in the transversal direction. By arranging a similar binding layer between the lling layer and the lower covering layerthere is Such a binding layer is arobtained in similar mannera binding in theY transversal direction ofthe last-mentioned layer,

While at the same time the binding of the lling layer is further amplified. e

The invention is illustrated on the accompanying drawing, Vwhich shows two embodiments of,

the invention. Figure 1 is a plan view and Fig-` ure 2 an end view `of boards according to one of the embodiments, while Figures 3 and 4 show, in similar manner, boards made in accordance with the other embodiment.

` construction of l the filling layer. In the shown example, the lling layer consists of a. number of mutually parallel lengths extending in the longitudinal directionof the board and arranged at a short distance from each other. They are provided with alternate incisions 2 cut from all of the four sides, the depth of said incisions being approximately two thirdsof the `thickness and width,` respectively, of the length so that all of the longitudinal bres'of the lengths are cutol. The incisions may, if desired, be cut `fromtwo op` posite sides only, preferably from the broad sides. The transversal e incisions prevent` effectively every tendency of the` board todistort or cast `by distortion of the lengths ofthelling layer." A

similar result may be obtainedby causingthe incisions to pass right through the length, in which case the lling layer will consist of a large number of short lengths arranged in rows. The boards are `rebated, longitudinal tongues3 and grooves 4 being provided in the outer lengths only,

, while transversal tongues 5 and grooves 6 are provided at the ends of all of the lengths. In order to prevent the longitudinal tongue 3 from being cut off by the incisions 2, the corresponding length isprovided with incisions from three sides only, the incisions cut from the upper sideand the lower side being made so `shallow that the tongue 3 is leit free. In similar manner, the cutting-through of the side walls of the grooves 4 may be avoided. In order toV further reduce the tendency of the outer lengths` to distort, these are preferably made narrower than the other rods.

The parquet veneer layer consists of parquet lengths l, all of which extend, accordingto the.,

shown example, in the longitudinal direction of the board. However, they may also be arranged in known manner alternately in the transversal direction and in thelongitudinal direction so as to form a checkered pattern. In the shown example, the lower covering layer 8 consists of a single uninterrupted veneer layer extending along the entire length of the board. It may, however, also consist of a plurality of thin laths or ribbons of veneer disposed side by side and extending in the longitudinal direction of the board.Y

Disposed -on each sidelof the lling layer and inside the parquet veneer layer and the lower covering layer is a binding layer 9 and IU, lrespectively, which consists of comparatively thin veneer and the run of grain of which extends in the transversal direction of the board. Each binding veneer layer is preferably made in a single piece of the same length and width as the board, but in any case it should extend without interruption in the tranversal direction of the board. All of the layers are interconnected by means of gluing. Preferably, the gluing-togther takes place in a. press under the influence of heat or pressure. In that oase, the parquet veneer layer is simultaneously exposed to a pressure in a lateral direction, which pressure is maintained until the glue has set. By this, `a rm cohesion laterally is obtained, which in turn entails that the parquet Veneer layer becomes highly resistant to the influence of humidity 'and dryness. Under such circumstances, the parquet lengths need not be glued together along the lateral edges. The lengths of the lling layer may also rest against each other along the lateral edges Vwithout being glued together at these edges, the edge surfaces being preferably lluted or provided with a` rough surface, for'i'nstance'by sawing the rods by means of a Asawv with coarse cut, so that the edges Ybecome to some extent yielding'to lateral pressure caused-by moisture variations.

As an example of the dimensioning ofthe boards andtheir various parts it may be mentioned Ath'at'the length of the boards may b-e 2 Yto 5 meters and their Width approximately l0 to l5 cm., 'while the thickness of the parquet veneer layer may be 5"to 8 mm., that the filling lengths approximately 20 min. andV that of the veneer longitudinal length or lath of the same length and width as the board, in which case, however, the board should not be given a greater Width than approximately 12 om., if the parquet veneer layer is made of teak or a similar kind of wood, and should be made still narrower, if a less dense kind of wood is employed. Also in this case there are employed two veneerilayers I'2,' I3, whic are arranged on either side. of the lling layer and the run of grain of which extends in the transversal direction. With a view to obtaining a sealing. joint between the boards, semicircular "channels I4 are arranged at the .sides of the outerlengths l5, I6 in which tow yarn or the like is introduced, a groove I1 also being arranged between the boards above the said channel'for introduction of a plastic jointing material. As the deck planks on board ships usually constitute the roof of the story below, the lower veneer layer I8' is suitably'made-thicker so: that it Inaybe given the desired sectional form.

'I claim: y j A` board particularly for flooring,^loomposedv of la* plurality of" Wood layers 'glued togethercomp'rising at leastthree diierent llayers,itheyupperm'ost of these layers being "a parquet' veneer layer'ormed of parquet veneerjrods,' the'second layer being an intermediate filling layer consisting of lengths extending in` the longitudinal' direc- "tion of (the board and 'atflea'st partially Acut throughin the transversal"direction"atY several places, the third layer being a bindinglayerarranged between'the parquet' veneerlayer `and the intermediate'layer and'consisting of' veneer "therun of grain of which 'extends'in the transversal 'direction of the board.

GUSTAF 

